Jamie Eng, of Woodend School, asks :-

How do different species start?

Michael Green, an anthropologist at the University of Otago, responded.

As an example, let's imagine that we live on the coast near the beach, and that there is a particular kind of seaweed that is found all over this coastline. All the seaweed is the same and it belongs to one species. Now, this seaweed loves salt water, and if we tried to put it into fresh water it would die.

However, let's imagine that a brand new river has found its way to the sea right where we live on the coast. A lot of fresh water from the river is now pouring into the sea, and the salt water environment that the seaweed is used to is changing to become a mixture of salt and fresh water. Over time, the seaweed near the river must change to adjust to the new environment, or it will die.

Now, let's jump forward in time a couple of thousand years, and have a look at the seaweed along our coastline. The seaweed living far away from the river mouth hasn't changed much at all, because its environment is still pretty much the same as in the past.

However, the seaweed living near the river mouth has changed quite a bit so that it can live in water that is not nearly as salty as the ocean water. This seaweed has changed so much that now it is a different species from the seaweed that used to grow here thousands of years ago.

When animals and plants change through time, they are said to be evolving. This is what evolution is all about. Our seaweed has evolved into a new species because its environment changed. Evolution can happen as a result of lots of different things, but new species starting because of changing environments is probably the most common.